Optical fiber communications systems utilize optical amplifiers such as, for example, erbium-doped optical amplifiers. These amplifiers can generate a significant amount of optical power within an optical fiber under normal operation conditions. In the event of a disconnected, broken, or cut optical fiber, hereinafter referred to as a cable disruption, there is the possibility that hazardous amounts of this optical energy can emerge from the disrupted end of the optical fiber. Optical energy emerging from the end of the optical fiber may be hazardous to the human eye under certain conditions. It is therefore desirable to detect a cable disruption to automatically shut down an optical amplifier until the condition is repaired, thereby possibly preventing an overexposure of a person's eye to the optical energy.
A need thus exists for a fail-safe system for use in a fiber-optic communications system for locally and automatically terminating operation of an optical amplifier or for reducing the output power level of the amplifier to a safe level without reliance on outside mechanisms to perform such a safety feature.